Available information suggests that acute gastroenteritis is a common illness in the elderly and may cause significant morbidity and mortality in this age group. The majority of these episodes of illness are of unknown etiology despite the application of conventional tests for bacterial pathogens. This suggests that fastidious viral agents may be involved, and although several such agents have recently been implicated in gastrointestinal disease in man, systematic studies to search for viral agents in the elderly have not been carried out. The few published reports available, however, suggest that the elderly may be unusually predisposed to infection with such agents. We, therefore, propose to determine the etiology, epidemiology and clinical features of acute gastroenteritis in the institutionalized elderly, with particular emphasis on the role of viral agents in this population. These studies will be carried out through prospective surveillance of a well defined group of elderly individuals. Clinical features and epidemiology will be determined by daily examination of ill individuals and by long term follow-up of outcome. The specific agents responsible will be determined by examination of diarrheal stool for the viral pathogens by utilization of newly described enzyme linked immunoassays (ELISA), radioimmunoassays (RIA), immune electronmicroscopy (IEM), and special tissue culture techniques, as well as by determination of seroconversion rates by ELISA, RIA and IEM. Diarrheal stools will also be examined for the presence of bacterial and parasitic pathogens by conventional techniques. Investigations of the relationship of certain host defense factors to susceptibility to viral gastrointestinal infections in the elderly will also be conducted. In addition, evaluation of selected control measures against viral gastrointestinal infections, such as vaccines against rotavirus, will be carried out in the elderly. The candidate is currently in his third year of infectious disease fellowship. His research interests have primarily been concerned with viral infections of the respiratory and gastrointestinal tract, and he has participated in several previous clinical studies involving elderly subjects in area nursing homes. The site of the proposed studies is a 634 bed chronic care facility closely affiliated with the University of Rochester. The proximity of this large, well characterized and stable population of chronically disabled elderly to an active, accomplished research group with a primary interest in viral gastrointestinal infections provides a unique environment for career development in the field of viral gastroenteritis in the elderly.